Metal bands are in particular used in the automotive sector as inlays for sealing strips to seal openings of the engine compartment, trunk or door. The continuously produced metal bands are jacketed by rubber and/or flexible plastic and have slots in order, among other things, to permit a penetration of the sealing material with metal bands not coated with an adhesive means, since the adhesion of rubber to metal or plastic to metal is not possible. On the other hand, metal bands coated with an adhesive means are very expensive. The metal bands can be advantageously manufactured by rotary cutting of the slots and subsequent stretch rolling of the metal band, namely without waste and at a high production speed.
The metal bands are bent to a usually U-shaped clamping section, which is clamped onto the sealing flanges of the opening before or after the jacketing with the sealing material. To allow the contours of the opening to be followed in this process, the clamping section must usually be flexible both in the horizontal and in the vertical plane. In addition, the clamping section should be compressible in the longitudinal direction, since the openings to be sealed can have substantial peripheral tolerances and a cutting to length of the sealing strip on site would be extremely time-consuming and/or expensive. Sealing strips having a compressible clamping section can namely preferably be produced endlessly to the maximum length which occurs and be compressed to the actual length on installation. Bonding or vulcanizing these sealing strips together or the like therefore does not have to take place on site so that the sealing strip installation can also be carried out by robots.
On the other hand, the clamping section must also have a specific tensile strength, since the trim strips or sealing strips are usually manufactured by extrusion, with substantial forces occurring in the longitudinal direction of the band. A further requirement of the clamping section consists of exerting a clamping force which is as large as possible on the sealing flanges.
Clamping sections of the named type are manufactured in that the metal band is continuously supplied to an extruder in which the sealing material lays itself around the metal band under the effect of pressure, said metal band subsequently being pressed out of the extruder through an opening whose shape is selected in accordance with the desired profile of the sealing strip. The finished clamping section must be cut to length to the precise dimension at the spout of the extrusion line. This is carried out by cutting processes such as sawing, grinding, mechanical cutting, laser cutting or plasma cutting. The difficulty exists in this process that a clamping section which continuously exits the extruder relatively fast has to be cut to length in a discontinuous workstep. The available time for the cutting through is therefore very short. In addition, materials with different properties have to be cut through simultaneously so that a high energy input is required.
A high energy input has the result that the materials which surround the metal band such as rubber, PVC and other sealants are impaired and the metal band is exposed too much. In addition to the visual degradation of the product, the risk of injury is thereby increased, on the one hand, and the vulcanizing together of the two ends of the sealing strip is made more difficult, on the other hand. There is the risk that the metal band will corrode with sealing strips which are not vulcanized or are vulcanized badly. The energy input must therefore be reduced by complicated and/or costly cooling.